var colors = ['green'];
var count = colors.push('red','blue');
console.log(count);//push方法返回的是数组的长度 3
console.log(colors);

var item = colors.shift();
console.log(item);//shift()方法获取第一项（列队先进先出）并移除
console.log(colors);

var count2 = colors.unshift('yellow');
console.log(colors);
console.log(colors.length);

var count3 = colors.pop();
console.log(count3);
console.log(colors.length);
